Back cushion



FIG. 1 is a first perspective view of a back cushion showing my new design;

FIG. 2 is a second perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a top plan view thereof. 

CLAIM The ornamental design for a back cushion, as shown and described. 